import math
x1, y1, x2, y2 = map(float,input().split())

n = (x2-x1)**2+(y2-y1)**2
N = math.sqrt(n)
print('{:.8f}'.format(N)) import math math x1, y1, x2, y2 = map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 n = (x2-x1)**2+(y2-y1)**2 n (x2-x1)**2+(y2-y1)**2 (x2-x1)**2 x2-x1 x2 x1 2 (y2-y1)**2 y2-y1 y2 y1 2 N = math.sqrt(n) N math.sqrt(n) math.sqrt math sqrt n print('{:.8f}'.format(N)) print '{:.8f}'.format(N) '{:.8f}'.format '{:.8f}' format N N = math.sqrt(n) math.sqrt(n) N y2 = map(float,input().split()) map(float,input().split()) y2 n = (x2-x1)**2+(y2-y1)**2 (x2-x1)**2+(y2-y1)**2 n x2, y2 = map(float,input().split()) map(float,input().split()) x2 x1, y1, x2, y2 = map(float,input().split()) map(float,input().split()) x1 y1, x2, y2 = map(float,input().split()) map(float,input().split()) y1
import math
x1, y1, x2, y2 = map(float,input().split())

n = (x2-x1)**2+(y2-y1)**2
N = math.sqrt(n)
print('{:.8f}'.format(N))
